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According to projects and practices that the Italian botanists and ecologists are carrying out for bringing “more nature in the city”, new insights for a factual integration between ecological perspectives and more consolidated aesthetic and agronomic approaches to the sustainable planning and management of urban green areas are provided.

Key message The article concerns the association between callose synthase and cytoskeleton by biochemical and ultrastructural analyses in the pollen tube. Results confirmed this association and immunogold labeling showed a colocalization. Abstract Callose is a cell wall polysaccharide involved in fundamental biological processes, from plant development to the response to abiotic and biotic stress. To gain insight into the deposition pattern of callose, it is important to know how the enzyme callose synthase is regulated through the interaction with the vesicle-cytoskeletal system. Actin filaments likely determine the long-range distribution of callose synthase through transport vesicles but the spatial/biochemical relationships between callose synthase and microtubules are poorly understood, although experimental evidence supports the association between callose synthase and tubulin. In this manuscript, we further investigated the association between callose synthase and microtubules through biochemical and ultrastructural analyses in the pollen tube model system, where callose is an essential component of the cell wall. Results by native 2-D electrophoresis, isolation of callose synthase complex and far-western blot confirmed that callose synthase is associated with tubulin and can therefore interface with cortical microtubules. In contrast, actin and sucrose synthase were not permanently associated with callose synthase. Immunogold labeling showed colocalization between the enzyme and microtubules, occasionally mediated by vesicles. Overall, the data indicate that pollen tube callose synthase exerts its activity in cooperation with the microtubular cytoskeleton.

In order to ascertain the role of plant transglutaminases (TGase) in growth and abiotic stress response, the AtPng1 knock out (KO) line of A. thaliana has been analyzed during plant development and under heat and wound stress. Comparing wild type (WT) and KO lines a 58-kDa band was immunodetected by anti-AtPng1p antibody in the cell wall and chloroplasts only in the WT line. A residual TGase activity, not showing correlation with development nor stress response, was still present in the KO line. The KO line was less developed, with a juvenile phenotype characterized by fewer, smaller and less differentiated cells. Chloroplast TGase activity was insensitive to mutation. Data on stressed plants showed that (i) KO plants under heat stress were more juvenile compared to WT, (ii) different responses between WT and KO lines after wounding took place. TGase activity was not completely absent in the KO line, presenting high activity in the plastidial fraction. In general, the mutation affected A. thaliana growth and development, causing less differentiated cytological and anatomical features.

Increasing temperatures, heat waves, and reduction of annual precipitation are all the expressions of climate change (CC), strongly affecting bread wheat (Triticum aestivum L.) grain yield in Southern Europe. Being temperature the major driving force of plants’ phenological development, these variations also have effects on wheat phenology, with possible consequences on grain quality, and gluten protein accumulation. Here, through a case study in the Bolognese Plain (North of Italy), we assessed the effects of CC in the area, the impacts on bread wheat phenological development, and the consequences on grain gluten quality. The increasing trend in mean annual air temperature in the area since 1952 was significant, with a breakpoint identified in 1989, rising from 12.7 to 14.1°C, accompanied by the signals of increasing aridity, i.e., increase in water table depth. Bread wheat phenological development was compared in two 15-year periods before and after the breakpoint, i.e., 1952–1966 (past period), and 2006–2020 (present period), the latest characterized by aridity and increased temperatures. A significant shortening of the chronological time necessary to reach the main phenological phases was observed for the present period compared to the past period, finally shortening the whole life cycle. This reduction, as well as the higher temperature regime, affected gluten accumulation during the grain-filling process, as emerged analyzing gluten composition in grain samples of the same variety harvested in the area both before and after the breakpoint in temperature. In particular, the proportion of gluten polymers (i.e., gliadins, high and low molecular weight glutenins, and their ratio) showed a strong and significant correlation with cumulative growing degree days (CGDDs) accumulated during the grain filling. Higher CGDD values during the period, typical of CC in Southern Europe, accounting for higher temperature and faster grain filling, correlated with gliadins, high molecular weight glutenins, and their proportion with low molecular weight glutenins. In summary, herein reported, data might contribute to assessing the effects of CC on wheat phenology and quality, representing a tool for both predictive purposes and decision supporting systems for farmers, as well as can guide future breeding choices for varietal innovation.

Nowadays, there is a wide range of different methods available for the monitoring of pollen and allergens, but their relative efficiency is sometimes unclear, as conventional pollen monitoring does not thoroughly describe pollen allergenicity. This study aims to evaluate airborne pollen, allergen, and protein levels, associating them with meteorological and chemical parameters. The sampling was performed in Bologna (Italy) during the grass flowering period, with three different devices: a Cyclone sampler (CS), a Dicothomous sampler (DS), and a Berner impactor (BI). Total proteins were extracted from aerosol samples, and grass allergens Phl p 1 and Phl p 5 were quantified by ELISA. Airborne Poaceae pollen concentrations were also evaluated, using a Hirst-type trap. Proteins and allergens collected by CS resulted about ten times higher than those collected by the other two instruments, possibly due to their different cut-offs, while DS and BI results appeared consistent only for the total proteins collected in the fine fraction (1.3 vs. 1.6 μg/m3). Airborne proteins correlated neither with Poaceae pollen nor with its aeroallergens, while aeroallergens correlated with pollen only in the coarse particulate, indicating the presence of pollen-independent aeroallergens in the fine particulate, promoted by high wind speed.

Although pollen structure and morphology evolved toward the optimization of stability and fertilization efficiency, its performance is affected by harsh environmental conditions, e.g., heat, cold, drought, pollutants, and other stressors. These phenomena are expected to increase in the coming years in relation to predicted environmental scenarios, contributing to a rapid increase in the interest of the scientific community in understanding the molecular and physiological responses implemented by male gametophyte to accomplish reproduction. Here, after a brief introduction summarizing the main events underlying pollen physiology with a focus on polyamine involvement in its development and germination, we review the main effects that environmental stresses can cause on pollen. We report the most relevant evidence in the literature underlying morphological, cytoskeletal, metabolic and signaling alterations involved in stress perception and response, focusing on the final stage of pollen life, i.e., from when it hydrates, to pollen tube growth and sperm cell transport, with these being the most sensitive to environmental changes. Finally, we hypothesize the molecular mechanisms through which polyamines, well-known molecules involved in plant development, stress response and adaptation, can exert a protective action against environmental stresses in pollen by decoding the essential steps and the intersection between polyamines and pollen tube growth mechanisms.

Allergenicity indices are a powerful tool to assess the health hazard posed by urban parks to pollen allergic subjects. Nonetheless, only few indices have been developed and applied to urban vegetation in the last decade, and they were never compared nor standardised over the same dataset. To address this issue, in this paper the two best-known allergenicity indices, the Urban Green Zones Allergenicity Index (IUGZA) and the Specific Allergenicity Index (SAI), have been calculated for the same park (the Botanical Garden of Bologna), collecting vegetation data through both systematic sampling and arboreal census. The results obtained with the two data collection methods were comparable for both indices, indicating systematic sampling as a reliable approximation of the total census. Besides, the allergenic risk resulted moderate to high according to SAI, and very low according to IUGZA. Since SAI does not consider the total volume of the vegetation, it was deemed less reliable than IUGZA in evaluating the allergenicity of an enclosed green space.

Pollinosis and allergic asthma are respiratory diseases of global relevance, heavily affecting the quality of life of allergic subjects. Since there is not a decisive cure yet, pollen allergic subjects need to avoid exposure to high pollen allergens concentrations. For this purpose, pollen forecasting is an essential tool that needs to be reliable and easily accessible. While forecasting methods are rapidly evolving towards more complex statistical and physical models, the use of simple and traditional methods is still preferred in routine predictions. In this review, we summarise and explain the main parameters considered when forecasting pollen, and classify the different forecasting methods in two groups: observation-based and process-based. Finally, we compare these approaches based on their usefulness to allergic patients, and discuss possible future developments of the field.

Understanding airborne pollen allergens trends is of great importance for the high prevalence and the socio-economic impact that pollen-related respiratory diseases have on a global scale. Pursuing this aim, aeropalynology evolved as a broad and complex field, that requires multidisciplinary knowledge covering the molecular identity of pollen allergens, the nature of allergen-bearing particles (pollen grains, pollen sub-particles, and small airborne particles), and the distribution of their sources. To estimate the health hazard that urban vegetation and atmospheric pollen concentrations pose to allergic subjects, it is pivotal to develop efficient and rapid monitoring systems and reliable allergic risk indices. Here, we review different pollen allergens monitoring approaches, classifying them into I) vegetation-based, II) pollen-based, and III) allergen-based, and underlining their advantages and limits. Finally, we discuss the outstanding issues and directions for future research that will further clarify our understanding of pollen aeroallergens dynamics and allergen avoidance strategies.

Transglutaminases (TGases) are calcium-dependent enzymes that catalyse an acyl-transfer reaction between primary amino groups and protein-bound Gln residues. They are widely distributed in nature, being found in vertebrates, invertebrates, microorganisms, and plants. TGases and their functionality have been less studied in plants than humans and animals. TGases are distributed in all plant organs, such as leaves, tubers, roots, flowers, buds, pollen, and various cell compartments, including chloroplasts, the cytoplasm, and the cell wall. Recent molecular, physiological, and biochemical evidence pointing to the role of TGases in plant biology and the mechanisms in which they are involved allows us to consider their role in processes such as photosynthesis, plant fertilisation, responses to biotic and abiotic stresses, and leaf senescence. In the present paper, an in-depth description of the biochemical characteristics and a bioinformatics comparison of plant TGases is provided. We also present the phylogenetic relationship, gene structure, and sequence alignment of TGase proteins in various plant species, not described elsewhere. Currently, our knowledge of these proteins in plants is still insufficient. Further research with the aim of identifying and describing the regulatory components of these enzymes and the processes regulated by them is needed.

In clementine, failure of fertilization can result in parthenocarpic fruit development, which has several advantages, such as seedless fruit, longer shelf-life, and greater consumer appeal. Recently, S-RNases have been identified in Citrus grandis, thus revealing that the self-incompatibility (SI) reaction relies on the S-RNase gametophytic mechanism. The fundamental role of environmental factors, mostly temperature, in determining the numbers of pollen tubes reaching the ovary is also well established in Citrus. In the present work, temperature-dependent pollen–pistil interactions in C. clementina were analyzed, focusing on several morphological aspects, as well as on polyamine (PA) content and the activity and distribution of transglutaminase (TGase), both reported to be involved in the SI response in pear and in pummelo. Results clearly indicate that temperature contributed to a different activation of the SI response, which occurs at optimal temperature of 25°C but was by-passed at 15°C. TGase activity was stimulated during the SI response, and it localized differently in the compatible and incompatible interaction: in compatible pollinated styles, TGase localized inside the style canal, while it was detected all around it in incompatible crosses. TGase localization and activity were congruent with the levels of soluble and insoluble conjugated PAs and with morphological evidences, which highlighted cell wall modification occurring as a result of SI.

Tomato (Solanum lycopersicum L.) is one of the most widely cultivated crops in the world. Tomato is a plant model and the relationship between yield and biotic/abiotic stress has attracted increasing scientific interest. Tomato cultivation under sub-optimal conditions usually negatively impacts growth and development; in particular, heat stress affects several cellular and metabolic processes, such as respiration and photosynthesis. In this work, we studied the effects of chronic heat stress on various cytological and biochemical aspects using the Micro-Tom cultivar as a model. Photosynthetic efficiency decreased during heat stress while levels of post-photosynthetic sugars (sucrose, fructose, glucose and glucose 6-phosphate) oscillated during stress. Similarly, photosynthetic pigments (lutein, chlorophyll a, chlorophyll b and β-carotene) showed an oscillating downward trend with partial recovery during the stress-free phase. The energetic capacity of leaves (e.g. ATP and ADP) was altered, as well as the reactive oxygen species (ROS) profile; the latter increased during stress. Important effects were also found on the accumulation of Rubisco isoforms, which decreased in number. Heat stress also resulted in a decreased accumulation of lipids (oleic and linoleic acid). Photosynthetically alterations were accompanied by cytological changes in leaf structure, particularly in the number of lipid bodies and starch granules. Prolonged heat stress progressively compromised the photosynthetic efficiency of tomato leaves. The present study reports multi-approach information on metabolic and photosynthetic injuries and responses of tomato plants to chronic heat stress, highlighting the plant's ability to adapt to stress.

Irrigation is fundamental for agriculture but, as climate change becomes more persistent, there is a need to conserve water and use it more efficiently. It is therefore crucial to identify cultivars that can tolerate drought. For economically relevant crops, such as tomatoes, this purpose takes on an even more incisive role and local agrobiodiversity is a large genetic reservoir of promising cultivars. In this study, nine local Italian cultivars of tomatoes plus four widely used commercial cultivars were considered. These experienced about 20 d of drought, either at vegetative or reproductive phase. Various physio-morphological parameters were monitored, such as stomatal conductance (gs), photosynthesis (A), water use efficiency (WUE), growth (GI) and soil water content (SWC). The different responses and behaviors allowed to divide the cultivars into three groups: tolerant, susceptible, and intermediate. The classification was also confirmed by a principal component analysis (PCA). The study, in addition to deepening the knowledge of local Italian tomato cultivars, reveals how some cultivars perform better under stress condition than commercial ones. Moreover, the different behavior depends on the genotype and on the growth phase of plants. In fact, the Perina cultivar is the most tolerant during vegetative growth while the Quarantino cultivar is mostly tolerant at reproductive stage. The results suggest that selection of cultivars could lead to a more sustainable agriculture and less wasteful irrigation plans.

Pollen-stigma interaction is a highly selective process, which leads to compatible or incompatible pollination, in the latter case, affecting quantitative and qualitative aspects of productivity in species of agronomic interest. While the genes and the corresponding protein partners involved in this highly specific pollen-stigma recognition have been studied, providing important insights into pollen-stigma recognition in self-incompatible (SI), many other factors involved in the SI response are not understood yet. This work concerns the study of transglutaminase (TGase), polyamines (PAs) pattern and metabolomic profiles following the pollination of Pyrus communis L. pistils with compatible and SI pollen in order to deepen their possible involvement in the reproduction of plants. Immunolocalization, abundance and activity of TGase as well as the content of free, soluble-conjugated and insoluble-bound PAs have been investigated. 1H NMR-profiling coupled with multivariate data treatment (PCA and PLS-DA) allowed to compare, for the first time, the metabolic patterns of not-pollinated and pollinated styles. Results clearly indicate that during the SI response TGase activity increases, resulting in the accumulation of PAs conjugated to hydroxycinnamic acids and other small molecules. Metabolomic analysis showed a remarkable differences between pollinated and not-pollinated styles, where, except for glucose, all the other metabolites where less concentrated. Moreover, styles pollinated with compatible pollen showed the highest amount of sucrose than SI pollinated ones, which, in turn, contained highest amount of all the other metabolites, including aromatic compounds, such as flavonoids and a cynnamoil derivative.

Transglutaminase (TGase:E.C. 2.3.2.13) catalyzes the acyl-transfer reaction between one or two primary amino groups of polyamines and protein-bound Gln residues giving rise to post-translational modifications. One increasing the positive charge on a proteins surface and the other results in the covalent crosslinking of proteins. Pioneering studies on TGase in plants started in the middle of the 1980’s but the methodology designed for use with animal extracts was not directly applicable to plant extracts. Here we describe radioactive and colorimetric methods adapted to study plant TGase, as well as protocols to analyze the involvement of TGase and polyamines in the functionality of cytoskeletal proteins.

Polyamines (PAs) are small molecules necessary for pollen maturation and tube growth. Their role is often controversial, since they may act as pro-survival factors as well as factors promoting Programmed Cell Death (PCD). The aim of the present work was to evaluate the effect of exogenous PAs on the apical growth of pear (Pyrus communis) pollen tube and to understand if PAs and reactive oxygen species (ROS) are interconnected in the process of tip-growth. In the present study besides natural PAs, also aryl-substituted spermine and methoctramine (Met 6-8-6) analogs were tested. Among the natural PAs, Spm showed strongest effects on tube growth. Spm entered through the pollen tube tip, then diffused in the sub-apical region that underwent drastic morphological changes, showing enlarged tip. Analogs were mostly less efficient than natural PAs but BD23, an asymmetric synthetic PAs bearing a pyridine ring, showed similar effects. These effects were related to the ability of PAs to cause the decrease of ROS level in the apical zone, leading to cell death, counteracted by the caspase-3 inhibitor Ac-DEVD-CHO (DEVD). In conclusions, ROS are essential for pollen germination and a strict correlation between ROS regulation and PA concentration is reported. Moreover, an imbalance between ROS and PAs can be detrimental thereby driving pollen toward cell death.

Transglutaminases (TGases) are ubiquitous enzymes catalyzing many biological reactions. The best-known TGase activity, namely the transamidation of specific proteins by polyamines (PAs), has been studied in plants to verify if TGase is a mediator of PAs mechanism of action to re-interpret some of PAs effects. Usually, the TGase activity is present at basal level in plant cells, but it can be induced by internal or external events or stresses, like rehydration, wounding, light, developmental differentiation and programmed cell death (PCD). Here, two models of induced growth are presented, namely pollen apical growth and dedifferentiation followed by reacquisition of the pluripotency of already differentiated cells. Moreover, PAs and TGase involvement during the differentiation and the activity of organelles and finally during the terminal organ differentiation or self-incompatibility-induced PCD are reported. In all of these models, TGase plays a role. The enzyme was detected in several cell compartments, like cytosol, chloroplasts and possibly mitochondria, microsomal fraction, cell wall and also extracellularly. The products of TGase catalysis, modified with PAs, mainly consist of high molecular mass complexes. Among the protein substrates until now identified we mention the cytoskeletal proteins, actin and tubulin, whose PA modification also affects their interaction with motor proteins and the dynamic of cytoskeleton. The most widely studied substrates are component of chloroplast photosystems, in particular light-harvesting complexes, whose modification is light dependent and whose differentiation and size are affected by TGase, thereby conditioning photosynthetic efficiency and photoprotection. Finally, modification of cell wall substrates affects wall growth and reinforcement.

Gluten is the major factor involved in the structural properties of bakery products. Thanks to its ability to create aggregates, it gives dough viscosity, elasticity and cohesion, all features responsible for the baking performance. Gluten is composed of extensible, viscous gliadins and rigid, elastic glutenins. Moreover, the gliadin protein fraction is the main factor responsible for the development of celiac disease (CD) and other non-celiac gluten sensitivities. The only treatment for these people is lifelong adherence to a strict gluten-free diet. Nowadays, the development of new technologies in the food industry aims to both improve products already marketed, and to develop new gluten-free products. Cross-linking enzymes, able to organize and create protein networks, are suitable for the food industry as protein modifiers. Among those enzymes, Transglutaminase (TGase) due to its ability to improve the firmness, viscosity, elasticity and water-binding capacity of food products could be the key factor for manipulation in order to achieve higher food quality. The aim of this study was to evaluate the effects of addition of microbial transglutaminase from Streptoverticillium mobaraense, on protein aggregation in gluten free flours as well as in baked products. In our research we assessed five gluten free flours deriving from different plant sources such as cereals, pseudo-cereals and legumes, in particular corn, rice, amaranth, quinoa and lentil flours have been analyzed. By biochemical tests, flours’ total extracted proteins capacity to act as TGase substrate was evaluated. Since all tested flours showed considerable transamidase activity in microplate colorimetric assay, the possible formation of crosslinked products were analyzed by SDS-PAGE. For this purpose, micro-doughs prepared by adding the water, in 1:2 ratio (w/v), to different flours were treated with different amount of TGase enzyme (0.5; 0.75; 1; 2 Units). To clarify which protein fraction of the flours was the best substrate for the TGase, differential extractions were performed. Therefore, three sequential fractions, corresponding to albumins/globulins, prolamins and glutelins, were analyzed in relation to different enzyme amounts. Results showed that the microbial TGase has capacity to modify gluten free flour proteins and determine protein network formation. In particular, lowest enzyme concentration (0.5 U) was able to cause differences in protein bands between treated samples and their non-treated controls. These preliminary results give a perspective in the gluten-free research and suggest their possible use to create innovative products with improved texture.

Gluten is the major factor involved in the structural properties of bakery products. Thanks to its ability to create aggregates, it gives dough viscosity, elasticity and cohesion, all features responsible for the baking performance. Gluten is composed of extensible, viscous gliadins and rigid, elastic glutenins. Moreover, the gliadin protein fraction is the main factor responsible for the development of celiac disease (CD) and other non-celiac gluten sensitivities. Nowadays, the development of new technologies in the food industry aims to both improve products already marketed, and to develop new gluten-free products. The purpose of our work was to set up a biotechnological process based on the combined use of cross-linking enzymes and selected microbial consortia to produce new gluten free bakery products with improved shelf-life, and sensory properties. Cross-linking enzymes, able to organize and create protein networks, are suitable for the food industry as protein modifiers. Among those enzymes, Transglutaminase (TGase) is surely a potentially interesting tool for its capacity to enhance the cohesiveness and elasticity of the dough, solving the problem of lack of consistency of gluten-free flours. Our research showed that the microbial TGase (from Streptoverticillium mobaraense) has the capacity to modify wheat flour proteins and determine protein network formation responsible for a major molecular structural stability of the product. The TGase effect on flour mainly involved gluten and globulin fraction modification. The results showed that the enzyme activity in the presence of a selected microbial consortium of lactic acid bacteria and yeasts (Lactobacillus sanfrancisciencis and Candida milleri) caused synergic effects on the sensory, rheological and shelf-life features of the products. These features resulted significantly affected also by formulation and process variables. Based on our results, we are evaluating the gluten-free flours of corn, rice, amaranth and lentil, to develop a new bakery product for people with gluten sensitivities.

Programmed cell death (PCD) is a process that occurs throughout the life span of every plant life, from initial germination of the seed to the senescence of the plant. It is a normal physiological milestone during the plant's developmental process, but it can also be induced by external factors, including a variety of environmental stresses and as a response to pathogen infections. Changes in the morphology of the nucleus is one of the most noticeable during PCD but all the components of the plant cell (cytoplasm, cytoskeleton and organelles) are involved in this fascinating process. To date, relatively little is known about PCD in plants, but several factors, among which polyamines (PAs) and plant growth regulators, have been shown to play an important role in the initiation and regulation of the process. The role of PAs in plant PCD appears to be multifaceted acting in some instances as pro-survival molecules, whereas in others seem to be implicated in accelerating PCD. The molecular mechanism is still under study. Here we present some PCD plant models, focusing on the role of the enzyme responsible for PA conjugation to proteins: transglutaminase (TGase), an enzyme linked with the process of PCD also in some animal models. The role of PAs and plant TGase in the senescence and PCD in flowers, leaf and the self-incompatibility of pollen will be discussed and examined in depth.

Fattori che influenzano la crescita apicale del polline nell’autoincompatibilità Iorio RA1, Aloisi I 1, De Franceschi P2, Dondini L 2, Cai G3, SansaviniS2, Serafini Fracassini D1, Del Duca S*1 1 Dipartimento di Biologia, Università di Bologna, Via Irnerio 42, Bologna (Italy), stefano.delduca@unibo.it 2 Dipartimento di Colture Arboree, Università di Bologna, 3 Dipartimento di Scienze Ambientali, Università di Siena La risposta di autoincompatibilità (SI) nella riproduzione sessuale delle piante è il sistema più importante per prevenire l’autofecondazione; dal punto di vista evolutivo si ritiene che il grande successo delle angiosperme sia dovuto, almeno in parte, all’affermarsi della SI. Questa risposta prevede l’interazione polline-pistillo ed un sistema di riconoscimento fra le cellule che regola l’accettazione o il rigetto del polline, così che quello incompatibile venga inibito selettivamente in stadi specifici durante l’impollinazione. Un aspetto intrigante della biologia riproduttiva delle piante è capire come questa risposta si manifesti e quali siano i protagonisti dell’ interazione polline-pistillo. Un ruolo chiave nella SI, almeno nelle Rosaceae, è attribuito al locus genico S dello stilo che codifica per una glicoproteina con attività ribonucleasica (S-RNasi) che entra nei tubetti in crescita bloccando quelli incompatibili (1, 2). Fra i fattori che potrebbero giocare un ruolo vi sono le poliammine (PAs) che sono essenziali per la crescita cellulare negli animali e nelle piante e che durante l’impollinazione dello stilo vengono rilasciate negli spazi intercellulari (3,4), probabilmente svolgendo un ruolo nell’interazione polline-pistillo (5). Per verificare questa ipotesi il polline germinante è stato trattato con diverse ammine; quelle che si sono dimostrate più efficaci sono la spermina (spm) ed il BD23 (un’ammina artificiale) che bloccano completamente la crescita del tubetto già alla concentrazione di 0.1 mM. Analizzando il contenuto delle PAs naturali nei pistilli impollinati con polline “self” o con polline compatibile si è visto che nei due sistemi il pattern di queste molecole varia sia in funzione del tipo di poliammina, sia che siano libere o legate. Il ruolo delle PAs nel tubetto pollinico non è stato ancora chiarito, ma sembra essere in relazione all’interazione con altre molecole ad es. proteine (7) e/o al metabolismo dei diversi RNAs ed al controllo dell’attività RNasica durante l’emergenza e la crescita del tubetto (4, 6). In Pyrus c., le PAs alifatiche libere sono più concentrate negli stili impollinati con polline compatibile rispetto a quelli con polline incompatibile. I risultati sono in accordo con una possibile inibizione dell’attività RNasica da parte delle PAs poiché un’inibizione dell’attività RNasica ha luogo nella SI (1). Il trattamento del polline germinante con una S-RNasi ricombinante (allele S105) blocca completamente l’allungamento del tubetto in circa il 50% dei pollini dimostrando che anche in Pyrus c. l’attività S-RNasica gioca un ruolo chiave. Inoltre, poichè in letteratura è riportato che le PAs possano avere un ruolo “scavengers” delle Specie Reattive dell’Ossigeno (ROS) (8), si è analizzato anche quest’aspetto. Si sa che i ROS sono prodotti fisiologicamente durante la germinazione e la crescita del tubetto (9,10) e quando la loro formazione viene inibita la crescita del tubetto si arresta. Utilizzando tests con l’NBT per mettere in evidenza i ROS nel polline germinante, abbiamo visto che la spm ed il BD23 alle concentrazione 0.1 mM inibiscono drasticamente la formazione di ROS lasciando ipotizzare un meccanismo in cui le PAs potrebbero agire controllandone la concentrazione nei tubetti in crescita. Bibliografia 1. McClure BA, Franklin-Tong V (2006) Planta 224:233–245 2. Di Sandro A, Serafini-Fracassini D, Del Duca S, ., et al. (2007) Acta Hort. 800, 423-426. 3. Bagni N, Adamo P, Serafini-Fracassini D, Villanueva VR (1981) Plant Physiol 68:727–730 4. Speranza A, Cal...